Changes in BDNF-immunoreactive structures in the hippocampal formation of the aged macaque monkey

We investigated the changes of brain-derived neurotrophic factor (BDNF)-imm unoreactive structures in the hippocampal formation of ;aged macaques (Maca ca fuscata fuscata). At adult stages (10 and 12 years), BDNF immunoreactivi ty occurred in the neurons of the dentate gyrus, the pyramidal neurons in t he CA1, CA2, CA3 subfields and the subiculum, and the neurons in the CA4 su bfield and the entorhinal cortex. The apical dendrites were also BDNF immun opositive. In aged monkeys (26, 30 and 32 years), the intensity of the BDNF -immunoreactivity declined significantly in cell bodies and dendrites of th e neurons in the hippocampal formation except the CA2 pyramidal neurons. Th ese findings indicate that BDNF is one of the vulnerable signal molecules d uring the aging process of the primate hippocampal formation. (C) 2001 Else vier Science B.V. All rights reserved.